Rod, I searched and searched without success. I did find a precancels.com site which might have this paper you mentioned. I found a reference to literature by Michael Hynes, but the site takes me to a dead end. At https://www.precancels.com/links/
down in the page there is a link to the Michael Hynes site that failed (it is called precanceled.com and the implication is that site is no longer in use). Not sure how much more digging I will do on these as I only have a handful of the roller type and I just finished mounting the 160+ precancels I have. These will just go into the binder behind the other Belgium pages. Thanks for all of your help!